Super-Telescope Placed in Orbit by Astronauts : Space: Equipment error delayed the deployment, but a spacewalk to correct the problem proved unnecessary.
The Hubble Space Telescope was set free to explore the heavens Wednesday.
The deployment climaxed a tension-filled day during which it looked for a while as though two astronauts aboard the shuttle Discovery would have to venture outside and free a balky piece of equipment. But that turned out to be unnecessary, and at 12:38 p.m. PDT, as Discovery sped over the Pacific Ocean and neared the West Coast, astronomer Steven Hawley gently released the $1.5-billion instrument from the shuttle’s robotic arm.
Moments later, Discovery commander Loren J. Shriver fired the small positioning jets on the shuttle and backed slowly away.
“She’s finally on orbit,” Richard H. Truly, chief of the National Aeronautics and Space Administration, said a few minutes later. “The first of NASA’s Great Observatories is now on station.”
The Hubble will be followed by three other space telescopes--one later this year and two others by the end of the decade--each designed to study the universe at different wavelengths of light.
For a time Wednesday, it appeared that astronauts Bruce McCandless, 52, and Kathryn D. Sullivan, 38, might have to leave Discovery to cope with a 40-foot-long solar panel that refused to unfurl. Ground controllers at the Goddard Space Flight Center here solved the problem when they ordered the telescope to ignore a sensor that had automatically stopped the unfurling.
The sensor indicated that the fragile panel was under such tension that it threatened to tear itself apart, but ground controllers determined that the sensor was faulty and overrode the automatic shut-off.
Moments later, the gold panel stretched out like a wing shimmering in the brilliant sunlight.
No sight could have been finer to the dozens of scientists who have worked for years on the space telescope project. The two solar arrays provide the energy to keep the telescope’s batteries charged, and without both of them in operation the telescope would not have had enough juice to maintain the heat needed to keep its delicate instruments from freezing.
Even the telescope itself would have been at risk if it had been impossible to deploy both solar arrays.
Orbiting 381 miles above the ground, the telescope is subjected to dramatic changes in temperature as it travels through sunlight and the darkness of the Earth’s shadow. The temperature plunges while the craft is in the shade, and unless the telescope is heated it could sustain serious damage, said Edward Weiler, program scientist at NASA headquarters.
“The structure can actually crack if it gets too cold,” he said.
For that reason, McCandless and Sullivan put on spacesuits and prepared to go outside. Both are veterans of spacewalks, and during an interview before the flight the white-haired McCandless acknowledged that he would like to make just one more spacewalk.
“I would like to do it,” he said earlier. “But I would not like the reason to be a failure with the telescope.”
He almost got his chance, and at an orbit that is about twice as high as the shuttle usually flies. Television images from the shuttle Wednesday showed the Earth as a distant blue-and-white globe, and a spacewalk would have been spectacular.
“I imagine Kathy and Bruce could just taste it,” Truly said after the bold venture became unnecessary.
The astronauts were part of the five-member Discovery crew that blasted off Tuesday from Kennedy Space Center in Florida to carry the space telescope, described as the finest optical instrument ever made, into orbit.
Partly because of the immense importance of the telescope, coupled with a number of minor problems that plagued ground controllers throughout the deployment, Wednesday added up to a “really stressful” day, said a normally subdued Mike Herrington, director of orbital verification.
But the troubles with the solar array were about the only serious problems that the astronauts faced.
However, even with the telescope floating freely around Earth, the Discovery crew was not quite ready to give up its stewardship over the Hubble. Discovery will remain within about 40 miles until sometime Friday so that it can zip back up if anything goes wrong.
Ground controllers will try out the telescope’s sophisticated maneuvering system today, and if they are satisfied that they have absolute control over the vehicle, they will pass another milestone sometime Friday--they will order the telescope to remove its lens cap.
The cap is designed to protect the telescope if it should accidentally point toward the sun, which would burn out some of the instruments, so controllers want to be sure the scope will respond to every command before removing the cap.
That should be a routine maneuver, but if for any reason the lens cap--called in the best NASA vernacular the “aperture door”--fails to respond to the command, Discovery will rendezvous with the telescope, and McCandless and Sullivan will finally get their spacewalk.
If all goes well, however, the shuttle will be freed from its responsibilities in time for its 6:49 a.m. PDT landing Sunday at Edwards Air Force Base, Calif.
In a few days, possibly as early as Tuesday, astronomers hope to capture their first image with the telescope, although it will be an engineering maneuver and the photo may be fuzzy. It will be several months before all the bugs are out, all the instruments have been calibrated and the Hubble assumes its place in history. It will spend 15 to 30 years studying the dimmest and most distant objects in the universe and is expected to provide a clarity never before seen by astronomers.
